After rebooting into the new kernel, systemd-udevd is no longer pegging the CPU, and is no longer writing log entries after the normal startup sequence. (As a side note, the system start time is now much faster.)

With this findings you should raise the issue at RHs bugzilla. If/when the fix the issue in their kernel, CentOS will inherit the fix.
I'll leave toracat to comment on the possibilities of including this fix in the plus kernel (if the exact fix can be localized).

By installing kernel-ml, you are testing the latest stable kernel from kernel.org. The CentOS kernel is built from the corresponding kernel from RHEL. The fact that kernel-ml works but not the CentOS kernel means the fix is present in the latest upstream (kernel.org) kernel but has not been backported to the CentOS (RHEL) kernel.